New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela E. Sanhueza1,2, R. Holzinger1,*, B. Kleiss1, L. Donoso2, and P. J. Crutzen1 1MPI für Chemie, Luftchemie, Postfach 3060, 55020 Mainz, Germany 2IVIC, Atmospheric Chemistry Laboratory, Apartado 21827, Caracas 1020A, Venezuela *now at Univ. Calif. Berkeley, Div Environm Sci, Dept. Ecosyst. Sci. Policy & Management, Berkeley, CA 94720, USA
Abstract. Using the proton transfer reaction mass spectrometry (PTR-MS) technique,
acetonitrile was measured during the wet season in a Venezuelan woodland
savanna. The site was located downwind of the Caribbean Sea and no biomass
burning events were observed in the region. High boundary layer
concentrations of 211±36pmol/mol (median, ±standard deviation)
were observed during daytime in the well mixed boundary layer, which is
about 60pmol/mol above background concentrations recently measured over the
Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is
released from the warm waters of the Caribbean Sea thereby enhancing mixing
ratios over Venezuela. Acetonitrile concentrations will probably still be
much higher in biomass burning plumes, however, the general suitability of
acetonitrile as a biomass burning marker should be treated with care.
During nights, acetonitrile dropped to levels typically around 120pmol/mol,
which is consistent with a dry deposition velocity of 0.14cm/s when
a nocturnal boundary layer height of 100m is assumed.
Citation: Sanhueza, E., Holzinger, R., Kleiss, B., Donoso, L., and Crutzen, P. J.: New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela, Atmos. Chem. Phys., 4, 275-280, doi:10.5194/acp-4-275-2004, 2004.